Aralkyl phenols as antioxidants



Patented Feb. 23, 1954 UNITE-D wires Are-NT omc-E 'He'nryJ; Kelie; Akron, Ohio, assignor to The B. F.

-Goodrich-ompany, New York,,N-. Y., a corporation of NewYork BN0 Drawing. :Applicat'ionlway 23, 15550, Serial-No. 163,806-

-10 Glaims.- (o1. 2150 4535) This intentionrelates to the preservation and firttecfionsr organic materials subject to deteii'ofat ibrr'afie to oxidation and other influences and-mere-specifiau -pertains to the incorporatin in rubber goods of certain 'aralkylated i-ccdmpounasrwhicn have been found to run" or: "therein as e tremely effective nonstaihirig fiii -ie'si'stirig "anti o'xilants-or age re sisters; I I

- as already been proposed-to employ-certain iecdmpounds such as phenoljcresols, tertiary utyl -phefiols, ro-sane iacid, hydroxydiphenyletlierfn pht-hol, d'inaphthol, i'riclene phe- ""'s',-'etc., as an "iiia-nts fer' rganii'c ifiaterials h ter idtd as mpose'fk'iy absorptiorr'of oxygen the' atniosphere. Cifieoi the most active ahtioiida nts of the phenolic type is the monobenzyl ether of hydroquinonefknown comrn'er- AgR'itefAlbaff qwever, phenolic e 'eswid sd a r befahtioxidants asa're certain more' efficient materials which are diaryl amines, and it has generally been thought thati'niproved"antioxidants must contain the diai yl'amine"str'uetiire.

I hai e no'wdiseo ieredthafcertain afalkylated phenols are highly effective 'antioxidants, being more eflicient and economical than either] the known pheneuc antidxidantser aie'rnorew uay fused diaryl amine-compounds. Accordinglmthis invention gem" r ses members 'j and compositions involving the breach a'raikyr phenolsas antioxidants for the preservation of organic substances which tfidtdfitiiite in the presence of oxygen including such materials as fishpil, linseed oil, tung oil, carotene, lubricating oils, animal fats, soaps and, "especially, rubfiei' y tinsaturatd'oi'ganicpolymricfnateriais.

The term frubbery; unsaturatedbigafiic poly- 'meric material isempl'oyezi to-incl'udalii'iatu'fal "and synthetic unsaturated 'fubbiy fit flyitdlitl materials and especially those which maybe-considered to be polymers of conjugated dieiies. *Examples of such rubbery materials include the various natural crude "waters (which are regarded as naturall'y 'occurring isoprene' ='poly- -ancl-such-synthetic rubb'ef-als pol" in of he, g methyl butadierie lgwand-ct ne-1,3 hydreearbensy-chloroprenefcyano. tiacliche-1,3 etc.,- as well as copolymers of these conjugated dienes with each'other or with other unsaturated compou'nds copolym'erizable therewith such as styrene, chlorostyrenes; isobutylene, acrylonitrile, methacrylonitrile, acrylic and'methacrylic acids, 'alkyl aci'ylates and metha'crylates, vinylidene' chloride, vinyl pyridine, etc.

Specific members oithe ar'alkylated phenol class of antioxidants orage resistors of thi's invention are,- for example, a-(l-phenylisopropyl) phenol, 2,4-di-(l-phenylisopropyb phenol, 2,4,6- tri-( l-phenylisopropyl) phenol, 4-(l-pheny1-lethyl) phenol, ZA-di (l-phenyl-l-ethyl) phenol, 'Zlfi-tti-(l-phenyl-l ethyl) phenol, 4-(1-p-tol- 'yl'isopropyl) phenol, 2,4-di-(l-p-tolylisopropyl phenol, 2,4,6-tri(l-p-tolylisepro'pyl) phenol, 4- (l-p-tolyl-I-ethyl) phenol, 2",4-di-(1-p-tolyl-1- ethyl) phenol, 2,4,6-tri-(l-p-tolyl-l-ethyl) phenol, 2 (1-phenyl-1-eth'y1) p'-c'reso1, 2,6 -di-(I- phhyl-l-ethyb p cres'ol, z-(l phenylisopropyl) p 'cresol, 2,6'-di-(l-phenylisopropyl) p-cresol, 5- rn'ethyl-2-(l -phenyl 1-ethyl) phenol, E-methyl- 2,4 (or 2,6) di-(l-phenyl-l ethyl) phenol, 5- methyI-Z-(-l phenylisopropyl) phenol, 5-methyl- 2,4(or 2,16) di-(lphenylisopropyl) phenol, 3- 'rnethyl-2 ,4,6-tri-tl phenyl-bethyl) phenol, 3- methyl-zAfiftri-(l-phenylisopropyl) phenol, 2- l phenylisopropyl) hydroquincne, 4- l-phenyli's j o pr'opyl) resorcinol, 4-; (l-phenylisopropyl) catech'ol, 2'-(I-'phenyl-1-ethyl) hydroquione, (1- phenyli'sepropyl) -3 hydroxy biphen'yl; 5 (1- phnylis iii'o'pyp 2 hydroxy biphenylyfi 1- efinyfisapiopyir-a naphthol, di (1 p-hen ylisopropyl) -2-naphtho1, 1- l phenyl-l-ethyl) -2- naphthol, and dil-phenyl-l-ethyl) -2-naphthol.

All these compounds' 'are aralkyl -phenols containing from one to -thr1earalky1 groups attached to the phenol nucleus and in which each aralkyl group consists of an aryl radical and an alkylidene radical of at least two carbon atoms, and has its connecting valence' o'n the same carbon atom of phloroglucinol, alpha-naphthol, beta-naphthol, etc., in the presence of a condensation catalyst such as A1013, HCl, BFz, concentrated sulfuric acid, and phosphoric acid. They can also be prepared quite advantageously by conducting the condensation in the presence of dilute sulfuric acid or a sulfonic acid catalyst as described in my copending application Ser. No. 163,808, filed May 23, 1950.

Aryl-substituted alkene hydrocarbons which can be condensed with phenols to produce the antioxidant compounds of this invention are those having the formula where Ar is an aryl hydrocarbon group and the R groups are hydrogen or alkyl groups. As specific aralkylene compounds which are suitable reactants there may be mentioned styrene, alpha-methyl styrene, p-methyl-alpha-methyl styrene, beta-methyl styrene, 2-methally1 benzene, allyl benzene, isopropenyl naphthalene, allyl naphthalene, propenylbenzene, and the like.

The reactants can be condensed in various ratios of the aryl-substituted alkene hydrocarbon to the phenolic compound, the use of 1 to 3 moles of hydrocarbon to one mole of phenol being preferred. The resulting condensation products generally contain a mixture of mono-aralkylated phenols, di-aralkylated henols and tri-alkylated phenols in proportions depending on the condensation ratio. In some instances, unreacted phenol and hydrocarbon as well as some polymerized hydrocarbon may also be present. To obtain the aralkyl phenolic compounds so prepared in sufiicient purity for use as antioxidant, it is only necessary to remove the unreacted aralkylene hydrocarbon and the polymers (generally dimers) of the aralkylene hydrocarbon. Better protection of oxidizable materials can be achieved through the use of a condensation product which has also had the unreacted phenolic compound removed that is, by employing only a mixture of aralkylated phenols. Still better antioxidants are secured by removing the monoaralkylated phenol so as to secure, as the final product, a mixture containing only diand tri-aralkylated phenols. Aralkylated phenolic compounds which are preferred as antioxidants in this invention are the products resulting from the condensation of styrene or alpha-methyl styrene or similar homologues of styrene with monohydric phenols having the formula Ar-OH, where Ar is an aryl hydrocarbon group having 6 to 10 carbon atoms. Thus, the preferred compounds are those which have the general formula ArOH where ture (12:2 or 3), mixtures thereof, and mixtures of mono-, diand triaralkylated phenols in which th di-aralkylated phenol is the most abundant and the mono-aralkylated phenol the least abundant ingredient.

In using the aralkylated phenolic compounds as antioxidants, they are incorporated, in any desired manner, with the oxidizable material to b protected. Only about 0.1 to 10% by weight of the antioxidant is generally sufficient to obtain adequate protection from oxidation. When used as non-staining, flex-resisting antioxidants for rubber goods, an amount from 0.5% to 5% by weight based on the rubbery material will generally give adequate protection.

The aralkylated phenolic compounds can be readily mixed with rubbery materials at the same time and in the same manner that vulcanizing or curing agents and other compounding ingredients ar added. This is the preferred method of incorporating these antioxidants with natural crude rubber, and results in the antioxidant becoming uniformly dispersed throughout the rubber composition. However, in the case of the synthetic rubbery materials, such as the copolymers of butadiene with styrene or acrylonitrile prepared by polymerization in an aqueous medium, it is most convenient to add the aralkylated phenolic compound in an aqueous dispersion or emulsion to the latex as it comes from the polymerization equipment. Then, when the polymer is recovered from the latex by coagulation or precipitation, the antioxidant is already uniformly incorporated throughout the mass of the rubbery material. The synthetic rubbery material will thus be protected from the time it is made as well as after compounding and vulcanization.

The specific examples described hereinafter will illustrate the antioxidant or age-resisting properties of aralkylated phenols with respect to the protection of rubbery materials. The term parts as employed in the examples is used to indicate parts by weight.

The alkylated phenolic compounds were employed in the examples in thre different composltions the recipes for WhlCh are given below:

COMPOSITION I (Oil-resistant white stock) Ingredient Parts Copolymer of 67% butadiene-l,3 with 33% acrylonitrile L... 97 Zinc oxide 5 Titanium dioxide 70 Stearic acid 1. 0 Dibutyl phthalate 15 Bis-(2-benzothiazyl) disulfid 1. 5 Sulfur l. 5

Antioxidant 1 as indicated- 1 100 parts of copolymer containing 3% antioxidant added during manufacture.

COMPOSITION II Natural crude rubber Carbon black Antioxidant as indicated.'.

'i- 'rhewulcanizable 1 rubbery compositionsrpreparediaccording -to the-above three-recipes *were heated for various periods of time and at 300 F. or 280 F. as shown below. Test strips of each 6 -I II,' -'and:-=the resulting mixture -was 'vfiilcanized at 280 F. The physical properties, before-and artr accelerated aging, the per cent retention or aging and the flex resi'stance after aging of the various vulcanizate were subjected to stress-strain tests. 5 'vulcanizates so obtained are tabulated below:

' Table I [Antioxidsnm-methyl-di-zitor 2,. 6)-(1-phenyl-1-ethyl) phenol] BEFORE some Composition I Composition III vulca ization Time? vulcanization Time r (Minutes) M T v E (Minutes) M T XVERAGET PERCENT RETENTION OF PHYSICAL PROPERTIES ON 'AGING T E T 'E 90 8s 71 68 m FLEX 'lEST-AGEI) SAIVIILES H I I k vulczfgiilziialtlilztigiP-imo F R VUIC%DI\ZIZiZEi(gS;UIIlG F R 40 112,500 3 40 140,000 z oo..- 65,000 3 some. 86,600 1 I 7 essentially consists of hanging test strips in large test tubes immersed ina heated oilbath and circulating fresh air inthetesttube. Ihis test is more fully described in theAS'IM test D865-48T.

Sdme 0f the agedteststripswere subjectedto "stress-strain tests.

Others of the aged test-stripswere subjected to flexing tests in the Delvlattia "Flexing Machine where the test strips were fiexed I out untilcrack growth had reached a rating of? where afratin'g of 0 represents now cracking and a rating of 10 represents complete break or failure.

.JIhe ratings were determined by a companiso'n'of .the crack growth with-established standards for,

each rating. In the: recitation of data appearing =in each illustrative example the followingabbrevviations have: th significance as indicated: T' is ultimate tensile strength in pounds per square inch, E is. percent elongation at break, M is the tensile-strength-at 300% elongation;Fis-thenum- --berof flex cycles for the rating-indicated, and -R the flex crack growthrating.

EXAMPLE I A disubstituted phenol, 5.-methyl-2,4( or 2I6) di- "'(11-pheny11-1-ethyl) phenol, .was employed as the antioxidant in Composition I. The resulting vul- .canizable mixture was vulcanized-at300' F. 5-

and the number of flexures were automatically counted and'recorded. The flex test was carried The above data demonstrates that 5-methyl- '2',4('or 2,6) -di-(1-phenyl-1-ethyl)-phenol is very "efiicient in protecting rubbery materials from deterioration by oxidation as evidenced by the high ercentage of tensile strength and elongation retained after the accelerated aging. 5-methyl- '2,4'(or 2,6) di (1 phenyl 1 ethyl) phenol also imparts a long flex life to articles prepared from "rubbery materials containing this compoundFas an antioxidant. Rubbery compositions :simi-lar to Compositions I and III except that they contain no antioxidant have very poor flex properties after accelerated aging. For example Composition III containing no antioxidant vulcanized for 66 minutes and aged as herein describedhas a flex rating of 3 at only 1750 flexures andla rating of 7 at only 3500 fiexures.

EXAMPLE II There Was employed as an antioxidant in Com- ;positions I and HI, a. mixture containing on a weight basis 15i4% 4-(1-phenyl-1-ethyl) phenol,

' 49%; 2,4 di (1 phenyl 1 ethyl) phenol and 35.6% 2,4,.6-tri-(l-phenyl-l-ethyl) phenol. This was the aralky-lated. phenol product resulting from the condensation of styrene with phenol in the mole ratio of 2 moles of styrene for each mole of phenol, after unreacted. phenol and styrene and styrene dimer had been removed. Composition I was vulcanized at 360 F., and Composition III- was vulcanized at 280 F. -"-I-he datablow shows the time of vulcanization. Stresssstrain tests were run-on test=samples-of each. vulcanizate before and after accelerated Casing 'Also 'fiex tests were-made ion agedftes t samples. The data from these tests are tabumercial non-coloring non-staining antioxidants lated below: as heptylated diphenyl amine and hydroqumone Table II iAntioxldant: Mixture of mono-,dland tri-aralkylated phenols] BEFORE AGING Composition I Composition III vulcanization Time vulcanization Time (Minutes) M T E Minutes) M E FLEX TEST, COMPOSITION III [After aging 48 hrs. 212 F.]

Antioxidant Present N o Antioxidant Sample Vulcanized, 280 F. for Min.

R F R F monobenzyl ether, when similarly employed, produce staining or discoloration.

The following tabulated examples will illustrate the effect on flex life and physical property retention of other members of the class of aralkylated phenolic compounds herein defined when used as antioxidants. These examples the recipes for Compositions I and II hereinbefore Show data obtained with vulcanizates set forth. The antioxidants employed were Pounded in the Composition I11 r pe, Vulca ed methyl-2,4(or 2,6) -di-(1-phenyl-l-ethy1)-phenol at 280 F. and aged 48 hrs. at 212 F.

Table III.E17ect of arallcylated phenols on flea: life and retention of physical properties after The above data clearly demonstrates that the 30 mixture of the mono-, di-, and tri-arallzvlated phenolic compounds protects rubbery materials from oxidation deterioration and imparts great- 1y increased flex life thereto.

EXAMPLE III White vulcanizates were prepared according to aging Flex Life Percent Example Compound Used as 233 7 5 Tensile N o. Antioxidant Min Strength F where R=3 F where R=7 Retained one 4D 7, 000 9, 500 24 None. 6O 1, 750 3, 500 4(1-1pheny11-cthy p g 5 110 7 1 2, 4 -hdi -(l -pheny] -l -ethyl) 70, 18?, w 75 p eno 2,4,g-tri-l(l-phenyl-l-ethyl) g8 g3, 13g, 72

p eno "i'fi f $3 12'838 2 %88 68 p e o 6 2,4-gi-(1iphenylisopropyl) 888 p eno 2,6-di (liphenyl-l-ethyl) 13g, 66

p-creso S-methyl-Z-(l-phenyl-l- 40 100,000 136, 600 71 ethyl) phenol. 60,000 76. 600 2-(1-phenyl1sopropyD- 40 97,500 125,000 73 2 tmelthlzliphefilol. 1 60 57, 500 65, 400 any 40 as 000 100000 propyl)-6-methyl-} Y 59 phenol. 60 0 46, 000

and the mixture of mono-, diand tri-(l-phenyll-ethyl) phenol described in Example II. Samples of the resulting four vulcanizates were tested for staining properties by placing them between both white lacquered and white enameled refrigerator panels for 96 hours at 80 0. None of the four vulcanizates caused staining of the white panels. Other samples of these four white rubbery vulcanizates were subjected to light discoloration tests and again no substantial discoloration was noted. However, such com- 76 aralkylated phenolic compounds impartagreater flex *life tmvnlcaniz'edrubberymaterials than'dd the mono-'ar'alkylated phenolic compounds; The examples tabulated in Tables IV-'and-*V *b'elow illustrate this variance-"in degree of antioxidant properties -between-- themono-,-, di and" tri aralkylated phenolic -compounds.-= Table..IV;-,Comparison. of. antioxidant properties of mono-, di-, andltri-aralkylatede phenolic compounds :in; white rubber compoundsavemge 1 Vulcanized at 300 F. 1 Vulcanized at 280 F.

Alli of thevaralkylated phenolic-"compounds used in the 'above examples are superior as anti oxidants to any of theaphenolic compounds heretofore suggested for suchuse. This is especially true where it is desired to have a rubbery product that will maintain .a high percentage of its physical properties throughout its useful life and still'be a non-'stainilig and substantiall'yjfree from discoloration. Also the antioxidants of this new class imparta longer-flex life to rubbery articles than do those of anyother class of phenolic compounds. Aralliylated phenolic compounds -.are equivalent. to mostof the ar-ylamine antioxidants employed ".in; rubber compounding. and-.possess the additional propertyof being none: staining and-'producing a rubber artiole sub'stan tially free from discoloration.

Having disclosed my inventionby 'means oi specific examples. and specific. chemical com: pounds, it is not my desire to limit myself solely. thereto, for as hitherto stated, the precisesproe portions of materials employed :mayr'beavaried Table V.C'omparison of antioxidant properties of mono-, di.-.... nd tri-aralkylated phenolic compounds in-treed compounds-Composition III,, aaedr48hou1ts at 212 F.

1 Vulcanized at 280 F.-

The above-data clearly show the superiority of the di-* and -tri-aralkylated 'phenoliccompounds (Exampl s 18 and ,19) over the mono-aralkylated phenol "(Example '17)" as antioxidants.

The following table illustrates the antioxidant effect of other aralkylate'd'ph'enolic compounds. The data isforcompositio'nsaged 48 hours at 212 which has been incorporated, as an antioxidant Table V! Percent Properties" ained Flexllife z Antioxidant Used Oompo- Composition Vule, sition I III 1 Time M E T F where R=3 F where R'--.7 Stain" 20 4-(l-p-Tolylisopropy1) Phenol 178 77 68 }None. 21 2,41- 1gi-(l1-p-Tolylisopropyl) 157 10 }None.

eno 22 3-Methyl-2,4,6-Tri-(lPheny1- 229 77 67 Do.

F l' 40 41300 49' 100 23 2,6-Dl-(IiPhGIIYIISOPI'ODYD- 197 76 55 Do.

p-creso. 24 Mixture of Monoand Di- 1- 191 77 56 Do.

phenyllsopropyl)-p-cresp1. 40 500 300 25 Mixture of Monoand D1- (1- 226 75 66 60 55'000 300 Do.

phenylisopropyl)-m-cres0l. 40 300 600 26 l-(l-phenylisopropyl)-2-Naph- 237 77 48 60 47300 56'700 Do.

I 7 t 40 63,800 74,000 27 l-(l-Phenyl-l-Ethyl)-2-Naph- 282 75 47 60 21 300 27 800 Do. 28 Di 2 l lheny1-l-Ethyl)-2- 204 41 g8 Do.

Naphthol.

1 Vulcanized at 300 F. 9 Vulcanized at 280 F. Test described in Example III.

11 therefor, from 0.1 to 10% by weight'of a polyaralkylated monohydric phenol of the structure It It wherein from 2 to 3 of the R groups represent aralkyl radicals of the structure where R. is selected from the class consisting of hydrogen and methyl, and the remaining R groups are selected from the class consisting of hydrogen and methyl, no more than one R group being methyl.

2. A rubbery composition comprising a rubbery unsaturated organic conjugated diene polymeric material in which has been incorporated, as an antioxidant therefor, from 0.1 to 5% by weight of a polyaralkylated monohydric phenol of the structure wherein from 2 to 3 of the R groups represent aralkyl radicals of the structure it B wherein from 2 to 3 of the R groups represent l-phenyl-l-ethyl radicals of the structure 12 and the remaining R groups are selected from the class consisting of hydrogen and methyl, no more than one B. group being methyl. f

4. A rubbery composition as defined in claim 3 in which the polyaralkylated phenol is di-2,4- (l-phenyl-l-ethyl) phenol.

5. A rubbery composition as defined in claim 3 in which the polyaralkylated phenol is tri- 2,4,6-(1-phenyl-1-ethyl) phenol.

6. A rubbery composition as defined inclaim 3 in which the polyaralkylated phenol is a mixture of 2,4-di-(l-phenyl-l-ethyl) phenol with a lesser amount of 2,4,6-tri-(l-phenyl-l-ethyl phenol).

7. A rubbery composition as defined in claim 3 in which the polyaralkylated phenol is a di- (1-phenyl-1-ethy1) cresol.

8. A rubbery composition comprising a rubbery unsaturated organic conjugated diene polymeric material in which has been incorporated, as an anti-oxidant therefor, from 0.1 to 5% by weight of a polyaralkylated monohydric phenol of the structure wherein from 2 to 3 of the R groups represent l-phenyl-isopropyl radicals of the structure Gin.

and the remaining R groups are selected from the class consisting of hydrogen and methyl, no more than one R group being methyl.

9. A rubbery composition as defined in claim 8 in which the polyaralkylated phenol is 2,4- dil-phenyl-isopropyl) phenol.

10. A rubbery composition as defined in claim 2 further characterized in that the composition is vulcanized.

HENRY J. KEHE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,989,788 Calcott et a1 Feb. 5, 1935 2,225,920 Martin Dec. 24, 1940 2,495,145 Smith et al Jan. 17, 1950 2,517,536 Chenicek Aug. 8, 1950 2.581,907 Smith et al Jan. 8, 1952 

1. A RUBBERY COMPOSITION COMPRISING A RUBBERY UNSATURATED ORGANIC POLYMERIC MATERIAL IN WHICH HAS BEEN INCORPORATED, AS AN ANTIOXIDANT THEREFOR, FROM 0.1 TO 10% BY WEIGHT OF A POLYARALKYLATED MONOHYDRIC PHENOL OF THESTRUCTURE 